Method of producing glass fibers



alm., EL, E9@ y, (300K T159 METHOD OF' PODUCING GLASS FIBERS Filed Nov. 13, 1945 5 4.Sheets-Shea?. l

INVENTQR EVERETTJ (100M` Jam my W5@ E. .1. comm METHOD OF PRODUCING GLASS FIBERS 3 Sheets-Sheet 2 Filed Nov. 15, 1945 ll'vvL-NTOR EVERHTJ. COOK,

\ 'i' l l Arramwm Jam., L 50 Filed NOV. 15, 1945 E. J. COOK METHOD 0F PRODUCING GLASS FIBERS 5 Sheets-Sheet 3 Ar-ramvevs Patented `lan. 31, 1950 METHOD 0F PRODUCING GLASS FIBERS Everett J. Cook, Toledo, Ohio, assigner, by mesne assignments, to Glass Fibers, Inc., Waterville,

Ohio

Application November 13, 1945, Serial No. 628,056

This invention relates to a method for producing glass fibers or filaments by mechanical draw,- ing of the laments under controlled conditions to obtain a uniform diameter of the drawn glass lament. The term :liber or filament as used in this application will refer to fibers that are of a diameter on the order of .@0025 and variations therefrom such as from .0001" to .0004", all of which fibers have 'been `drawn by controlling the variables of the controllable conditions under which `the glass fibers are drawn, all of which will be hereinafter more fully disclosed.

One of the principal objects `of the invention is to provide a method for mechanically drawing glass fibers or filaments wherein the conditions under which the fibers are drawn are accurately controlled to obtain a drawing of the fibers at a .uniform and constant diameter.

Another object of the invention is to provide a method Afor carrying out the foregoing object wherein a small body of molten glass has a pressure differential established upon opposite sides of the body of glassto cause the molten glass to exude through a plurality of small orifices to establish globule-like reservoirs of `molten glass beneath the orifices from which the are mechanically drawn.

It is still another object of the invention to provide a method for accomplishing the foregoing objects wherein the pres-sure differential established upon the body of molten glass and the temperature of the molten glass as well as the rate at which the fibers are mechanically drawn are maintained relatively constant after the `proper operating conditions have 'been established to obtain a predetermined size filament and thereby maintain the diameter of the filament relatively constant While it is continuously being drawn.

It is still another object of the invention that glass fibers 12 Claims. (Cl. L9-83.1)

in accomplishing the foregoing objects one' or more of the variable conditions'under'which the glass fibers are mechanically drawn can 'be changed to effect a change in the diameter of the filament being drawn without requiring a stoppage of the continuous mechanical drawing of the fibers to thereby readily shift fromone size fiber to another during a drawing of the fibers.

It is still another object of the invention that in accomplishing the foregoing objects, a body of molten.A glass is maintained at a substantially predetermined volume by continuously or intermittently feeding glass stock to the body of molten glass in response to a volume change in thebody and thereby maintain a relatively constant source of supply for establishing the globule-like reservoirs on the discharge side of a plurality of oriflces in a container through which the glass erudes from the container, l

These and other objects will become more apparent from the drawings and the following rde scription.

It is still another object of the invent-ion to correlate such factors as temperature of the molten glass, pressure differential upon the body of molten glass, speed of mechanically drawing the fibers, and site of orifice or aperture through which the molten glass is exuded to obtain `a determined diameter of drawn glass fiber and after such correlation to maintain the factors constant and thereby maintain a constant diameter of the ldrawn fiber.

In the drawings:

Figure 1 is a somewhat schematic illust-ration of apparatus for drawing glass `fibers in accord'- ance with this invention, and illustrates one form of a furnace for heating glass stock.

`Figure 2 is an enlarged cross-sectional view of the orifice plate of the furnace and illustrates the globule-like reservoirs that are established from which glass fibers are drawn.

Figure 3 is a schematic electrical system for operating the apparatus illustrated in Figure l.

Figure 4 is a somewhat schematic illustration of a modified arrangement of the apparatus illustrated in Figure 1 wherein the pressure differential upon the body of molten glass is obtained by use of a low pressure or vacuum .source in-4 stead of a pressure source as disclosed in Figure l.

Figure 5 is a perspective View partially in crosssection, of an apparatus for obtaining pressure differential upon a body of molten glass by means of centrifugal force.

In this invention, the glass fibers or filaments are drawn mechanically from a Supply or body of molten glass in such a manner that the diameter of the filaments is accurately controlled. Preferably, a plurality of fibers are drawn simultaneously, all under the same controlled conditions to thereby provide for a bundling or group ing of the fibers upon a suitable reel or spool from which the fibers can subsequently be re moved for manufacture into thread or yarn.

Thereis a peculiar quality in glass in the manufacture of glass fibers or filaments, in that the tensile strength of the glass fibers is increased as the temperature at which the glass fibers are drawn is reduced. However, as the temperature of the glass is reduced in an endeavor to obtain the higher tensile strength in the glass fibers, many difficulties have been encountered in properly controlling the diameter of the fibers or filaments to obtain absolute uniformity thereof. In this invention, however, the glass fibers or filaments are mechanically drawn under controlled conditions under which the lowest possible temperature of the glass consistent with good drawing qualities, is used. Preferably, the body of 'glass is heated within a metal furnace by conduction and radiation from the walls thereof, which walls are heated inductively by the use of high frequency energy. The temperature of the furnace is accurately controlled to maintain a predetermined condition of fluidity of the molten glass in the furnace so that a predetermined pressure differential applied upon the body ci molten glass will cause the molten glass to exude through a plurality of orifices in one wall of the furnace at a predetermined rate and thereby allow fibers or filaments to be drawn from globe ule-like reservoirs 'established at the outlet of each of the orifices at a predetermined rate to establish a predetermined size filament.

By controlling the temperature of the furnace, and thus the fluidity of the molten glass therein, the pressure differential upon the molten body of glass, the size of the orifices in the wall of the furnace and the rate at which the fibers are drawn, the diameter' of the drawn filaments can Y be controlled and varied to meet any requirement.

An apparatus for mechanically drawing glass fibers under controlled conditions in accordance with this invention is illustrated in Figures l, 2 and 3. VThis apparatus consists of a furnace it that has a crucible ll that holds a body of molten glass l2. The crucible il is constructed of a metal, preferably of a non-oxidlzable nature, at the high temperatures at which the metal is worked, which in this invention will be from 2200o F. to 2300" F., as preferable temperature. Such a metal is found in platinum or in platinum rhodium alloys.

The crucible il is provided with an aperture plate I3 that forms the bottom wall thereof. This aperture plate, more clearly illustrated in Fig. 2, has a plurality of apertures lil therein, which apertures are formed in prctrusions l that extend downwardly from the aperture plate I3. The molten glass within the crucible H exudes from the apertures i4 under controlled conditions hereinafter referred to and forms globule-like reservoirs of molten glass le at the end of each of the apertures i4. The glass filaments or nbers il have their genesis in the globules l5 and are drawn therefrom by a mechanical means hereinafter referred to.

The crucible l! is of relatively small size and has a high frequency coil i8 positioned around the same. This coil lll may consist of a tubular member such as copper, under which conditions the tubular member i8 will have water circulated therethrough to retain the same at a relatively low temperature and avoid melting of the tube due to radiation from the walls of the crucible Il. However, the coil lll may be constructed from a small platinum tube, under which conditions it will not be necessary to cool the tube, and some loss due to radiation from the crucible il is thereby avoided. The high frequency coil I8 is adapted to be connected to the outputof a high frequency generator or oscillating unit, such as the simplified form of such unit illustrated in Fig. 3, hereinafter more fully described, for impressing a frequency of 1.5 megacycles cn the coil lt, which frequency has been found most favorable for heating the platinum crucible il.

The crucible ll is secured upon the end of a ceramic tube 2s that has an opening 2l therein to receive the glass stoel; 22. rlhe opening 2| in the ceramic tube 2d may be provided with a platinum alloy lining 23 to prevent spalling andiiaking of the side wall of the tube 2d and thus avoid contamination in the molten glass body l2.

The glass stock E2 is preferably in what may be termed strip form, which in thisinstance takes the form of a rod that is fed into the Crucible ll under suitable control for maintaining the volume of the body of molten glass i?. in the crucible Il substantially constant at all. times. It is, of course, understood that when using the term strip in connection with the glass rod this invention, the term includes such other forms of glass as tubes, strips, whether continuously to the furnace or fed in pieces that may be tacked together.

The upper end of the ceramic tube 20 is provided with a resilient sealing member 24 that is adapted to engage the glass strip 22 to seal against the same and thereby close the interior of the crucible ll and the opening 2l in the tube 20 so that a gaseous pressure may be maintained in the crucible Il.

The ceramic tube 2li has an opening 25 through I the side wall thereof that communicates with an annular recess 25 provided in the heat insulating wall 21 surrounding the tube 2l). This annular recess 26 connects with an opening 28 Yin the wall 21 that connects with a pressure supply conduit 29 through which gaseous pressure is supplied into the interior of the tube 20 and the crucible |l. The pressure supply conduit 29 is connected to a suitable source of pressure 30 that is maintained relatively constant in any desired manner.

A control valve 35 is placed in the supply conduitZS to regulate the value of the pressure applied into the interior of the crucible il, and to regulate the pressure within the crucible Il constantly at a substantially predetermined value. The pressure reducing and control valve 35 may be of conventional and standard form that is adjustable for regulating the pressure in the outlet side thereof. A gauge 36 may be provided for indicating the pressure that is applied within the interior of the crucible Il. Also, a shut-off valve 31 may be located in the supply conduit 29 for shutting off the gaseous fluid supply, if desired. Y

It is, ofcourse, to be understood that when referring to gaseous fluids for supply into the crucible that any of the'conventional fluids are to be included such as air, the inert gases, or in some instances it may be desirable to utilize a gas such as hydrogen.

The glass strip 22 is fed into the crucible I| by means of a pair of rolls 4i! that are driven by an electric motor 4| through means of the gears 42 and 43. Operation of the motor 4| is controlled by the level of the glass body l2 in the crucible ll to feed the glass strip 22 at the desired rate to maintain the level of the body of molten glass substantially,T constant. The motor 4| is connected with suitable electric controls 1o accomplish the foregoing operation, which electric controls have one terminal thereof connected to the terminal 45 which engages the plate 46 carrying the contact rod 4l that passes downwardly through the ceramic tube 20 with the end 48 thereof in a predetermined position within the crucible ll. The crucible is engaged by a contact member 49 that is connected to the opposite terminal of the electric controls for operating the motor 4|.

The furnace I0 is also provided with a temperallure-sensitive device 50 for controlling the output of the high frequency oscillator to the coil I8, and thus control the temperature of the crucible Il. The temperature-sensitive device 50 is in effect a mercury thermometer having the three terminals 5|, 52 and 53 passing thereinto into engagement with the mercury column 54,

The terminal l is a common terminal or ground connection. The upper terminal 53 controls the output of the oscillator in a manner hereinafter described to maintain the temperature of the crucible ll substantially constant. The terminal 52 also controls the oscillator, and is adapted to cut in a stand-by tube in case the temperature of the crucible l l should drop below a predetermined value .for some accidental or unusual reason.

The electrical system for controlling the temperature of the Crucible il, and for controlling the feeding of the glass strip 2?. is more particularly illustrated in Figure 3 wherein there is shown a simplified form of high frequency oscillator. In the electrical Wiring diagram shown in Figure 3, there is illustrated a full Wave rectifier 5) having the output terminals 5| and E2 thereof. An oscillator or high frequency generator 7l) is connected to the output terminals El and B2 of the rectifier 60. The high frequency generator may consist of a conventional oscillating circuit to obtain the desired frequency on the output side thereof for delivery to the high frequency coil i3. As illustrated in Fig. 3, the high :frequency generator may consist of an oscillator tube Tl and a stand-by oscillator tube 'l2 that are supplied with current from the rectifier 6U. One side of the transformer 'i3 is connected to the anode le of the oscillator tubes li and l2, and the other side of the transformer 'i3 is connected with the cathodes l5 of the oscillator tubes H and l2 in conventional manner in cooperation with the rectifier 6D. The secondary coil 16 of the transformer 'I3 has the opposite terminals thereof connected with the opposite terminals of the high frequency coil I8 for thereby transmitting the energy of the high frequency generator to the high frequency coil. The grid-exciting coil'l'l, that may be a compound winding in the transformer 73, supplies the grid circuit of the oscillator tubes H and 12, and by varying the voltage in the grid circuit of the oscillator tubes 'H and l2, the output of the oscillator 10 is thereby controlled. Such a control of the grid circuit may be had through the potentiometer 18. The grid circuit of the oscillator tube 'H is continuously in circuit while the grid circuit of the oscillator tube 72 is provided with the contacts B1 that are operated by the relay coil B that is placed in Vcircuit with the terminal 52 of the temperature-sensitive device 5D. The contacts B1 are opened when the relay B is energleed, which is a normal condition, thereby allowing the tube l2 to actas'a stand-by tube.

The potentiometer 'l of the high frequency generator 'it is adapted to float over the resistance element thereof to control the output of the generator as this potentiometer is caused to operate by the electric motor lill. The electric motor 8 is adapted to cause the potentiometer to move in one direction and a torsion spring 8l connected to the shaft between the motor 80 and the potentiometer 'I8 is adapted to cause the potentiometer to move in an opposite direction. The direction of movement of the potentiometer to vary its resistance is controlled by the position of the mercury column 5d in the temperature-sensitive device with relation to the terminal 53 thereof. When the mercury column 5tengages the terminal 53 or is above the same, an electric circuit will be made through the relay coilA which closes the contacts A1 and thereby .energizes the motor BB to actuate the potentiometer 'I8 and reduce the output of the high frequency generator 1U. Conversely, when-the mercury column 54 is below the upper terminal 53 of the temperature-sensitive device 10, the relay coil A will be de-energized, thereby de-energizing the electric motor 86 and allowing the torsion spring 8| to actuate the potentiometer 18 in the opposite direction and thereby increase the output of the high frequency generator 10. It will thus be seen that the temperature-sensitive device 5i] will thus control the output of the high frequency generator Hl with suiciently close accuracy as to maintain the temperature of the Crucible l i at a substantially constant value. The preferable temperature conditions involved are approximately 2250 F. plus or minus 10 F.

As previously mentioned, the oscillator tube 12 acts as a stand-by tube, and assuming the apparatus is in operation, the mercury column 54 of the temperature-sensitive `device 5u will be above the terminal 52 thereof thus maintaining energized the relay coil B through the holding circuit contacts Bs that are closed, thus holding the contacts B1 open to render the grid circuit of the tube 12 ineffective. Should the temperature of the crucible Il fall sufficiently low that the mercury column of the temperaturesensitive element Sil disconnects with the terminal 52, the relay coil B will be cle-energized, thus allowing contacts B1 to close to out in the second oscillator tube 'l2 and thus quickly and substantially increase the output of the high frequency generator TE! to overcome the abnormal condition.

The electric motor @li for feeding the glass strip 22 into the furnace l@ is normally rendered active by the normally closed contacts C1 of the relay C, the relay C being cle-energized as long as the body of molten glass is out of engagement with the end 48 of the contact rod 4l. However, when the level of the molten glass reaches the end t8 of the contact rod al, electric circuit will be made through the now conductive body of molten glass to energize the relay C and thus open the contacts C1 to de-energize the motor Il l' and thus stop feeding of the glass strip 22. `In the electric circuit in Fig. 3, the` contact element 4l is illustrated by the switch 41a.

The filaments or bers ll are mechanically drawn by a reel or spool 9o that is suitably carried upon supporting hearings. This spool or reel Sli is driven by an electric motor 9i through means of .a variable speed mechanism 92, the variable speed mechanism being provided for establishing and maintaining any desired speed of rotation of the reel or spool lll.l

The fibers l1 are collected together and are adapted to pass through a guide ring 9.5 to collect the bundle of fibers upon thereel or spool el). The speed of rotation of thespool or reel e!! is one of the governing factors for controlling the diameter of the nlaments or fibers ll'.

There are four principal factors which govern the diameter of a fiber or filament during the drawing thereof, and which factors must be correlated `to obtain a desired filament diameter, and after correlation of the factors, they must remain constant thereafter during the drawing of the filament to maintain the diameter of the filament constant. Those four main factors are (l) establishing a predetermined temperature of the molten glass from which the fibers are drawn maintaining the temperature constant thereafter, (2) establishing `a pressure differential upon opposite sides of the body of molten glass in the furnace correlated with the temperature. .ofthe glass to exude the molten glass through the orifices in the orifice plate at a predetermined rate and maintain the pressure differential constant during the drawing operation, (3) establishing a rate of drawing the fibers from the molten glass at the ends of the orifices that is correlated with the temperature of the glass to mechanically draw the fibers to a predetermined degree of fneness as established by the rate of draw and thereafter hold the rate of draw constant during the drawing operation, and (4) establishing a predetermined size orice in the orifice plate correlated to the temperature of the molten glass in the Crucible and the pressure differential established upon that body of glass to permity passage of the molten glass through the orifice at just asuflicient rate to allow drawing of the fibers from the molten glass as it exudes through the oriiice at the predetermined rate established by the mechanical drawing means and still retain a reservoir of molten glass at the orifices from which the fibers can be drawn.

In the apparatus disclosed herein a predetermined pressure is maintained upon the body of glass in the crucible II which establishes the pressure differential previously Ireferred to upon opposite sides of the body, that is, the top and bottom thereof since the top surface of the body of glass is under pressure and the lower surface is at atmospheric pressure through the orifices f4, whereby the molten glass is exuded through the nozzle orifices I4 at a predetermined rate. It will readily be appreciated that the fluidity of the body of glass in the Crucible Il greatly affects the rate at which the glass exudes through the orifices I4, hence the temperature of the molten glass is established and maintained at that temperature satisfactory for proper delivery of the glass through the nozzle orifices to establish the globule-like reservoir I beneath the orifices lll.

Assuming that the rate of drawing of the fibers is constant and all other factors previously mentioned are constant except the pressure applied upon the body of molten glass to establish the pressure differential, the eifect of a change in the pressure differential is illustrated in the experimental results set forth below wherein the temperature of the glass body in the Crucible ll was maintained at 2230" F. plus or minus 20 ll'. and the speed of drawing of the iibers was 4.000 feet per minute through .035 aperture openings.

Air pressure Diam. fiber, lbs. drawn ins. of water inches per hour A second test in which the aperture openings were .040 gave the following tabulated results:

Air pressure Diam. liber, lbs. drawn ins. of water inches per hour From the foregoing it will be apparent that with three of the afore-mentioned factors constant, the pressure upon the body of molten glass, and thus the pressure dierential, has a direct bearing upon the diameter of the filament that is drawn, an increasing pressure causing a greater ii^w of molten glass which is taken up in the v.ent by an increased diameter thereof.

With all factors remaining constant except the .temperature of the body of glass in the Crucible i l, the following test results were obtained when using .000 apertures, an air pressure of 6" of water and a speed of drawing of 4,000 feet per From the foregoing, it will be apparent that as the temperature of the glass decreases, the diameter of the filament drawn becomes smaller tending to retard the movement of the glass through the orifices tsl in the orifice plate I3.

.es previously mentioned, the rate at which the fibers are drawn from the reservoirs at the orifices affects the diameter of the liber, as does the diameter of the orifice f4 in the oriiice plate I3. In the following tabulated test results that were obtained from tests to determine what effect the rate of draw and the size of orifice would have upon the filament diameter, the rate of draw is set forth en the basis of R. P. M. of a 2" spool which. at 7560 R. P. M. effects a rate of draw of approximately 4,000 feet per minute. The tempera-ture of the glass was held to 2230 F. and the air pressure on the molten glass was held t0 32" .of water. Three separate tests were conducted, using three different-size apertures in the aperture plate I3, namely, .040", .035", and .030". The R. P. M. of the spool was repeated for each test with each size aperture opening, as indicated in the tabulated results: Y

R. P. M. Av. diam.

2 spool ber .040" APERTURES .035" APERTURES i030" APERTURES From the foregoing results it will appear that the rate of draw affects the filament diameter when all other factors are maintained constant, and that the size of the orifices will also affect lament diameter when other factors are held constant.

In all of the tests that established the various foregoing results, the aperture plate contained 60 apertures.

To average all of the results, it has been found that to obtain a filament diameter of 00025", the most favorable conditions are to hold the temperature of the molten glass in the crucible I I at 2250 F. plus or minus 10 F. with the size of the orifices in the orifice plate of .040 plus or minus .005. The pressure established upon the body of the glass in the furnace is equal to `i" of water in a water column `gauge plus or minus of Water, with a rate of draw of the filaments at approximately 10,000 feet per minute. The above average conditions will maintain filament diameters of the desired size plus or minus .0000.2. Filament diameters of from .0001" to .0004 can be drawn by varying the variable factors as indicated herein. t

While the method and apparatus heretofore described with regard to Figs. l to 3, inclusive, has set forth the pressure differential upon the body of molten glass in the Crucible as being that occasioned by a positive pressure Within the Crucible, yet this pressure differential can be obtained in other ways such as that illustrated in Figs. e and 5.

In Fig. e there is illustrated a method of obtaining a pressure differential upon the body f molten glass in the Crucible by producing `a pressure area of less than atmosphere below ,the orince plate of the Crucible. Since the apparatus disclosed in Fig. fi is identical with that described heretofore, with the exception of the means for establishing the low pressure area adjacent the orifice plate, the numerals applied upon the apparatus of Fig. 4 are the Same as the numerals applied upon the apparatus illustrated in Fig. l but with the suffix a added thereto. t

In the apparatus of Fig. 4, the furnace Ia is provided with an enclosure Wall |00 around the lower portion thereof which has an opening `I0] therein adjacent the guide ring 95a through which the fibers or filaments may be ydravvnby the rcel or spool Sd. The enclosure Wall |00 is provided 'with a conduit lili! that connects the enclosure Within the enclosure Wall v|00 with a source of suction pressure, such as a vacuum pump i$l3 to `produce a pressure less than `atmosphere within the enclosure 505.

The Crucible lia is `in this instance open to the atmosphere through `a port passagelil `provided in the Wall of the furnace Ica. Thus, with the enclosure E05 maintained at a pressure less than atmosphere, a pressure differentialis established upon the body of molten glass i2c within the Crucible i ia tending to move the molten glass through the nozzle orifices lila in the same man ner as the positive pressure applied lWithin the Crucible II urges the molten .glass through vthe nozzle orifices is. By varying the sub-atmosphere pressure within the enclosure I 05, the pressure differential upon the body of molten glass may be varied to control the rate of ,movement thereof thro-ugh the nozzle orifices I4.

In Fig. 5 there is illustrated an apparatus whereby the pressure differential `upon the body of molten glass in the Crucible may b efobtained by centrifugal forcej and wherein the movement of the furnace to obtain the action of centrifugal force upon the body of molten glass therein aids in the drawing of the glass fibers or filaments.

In the apparatus of Fig. `5, a pluralityof individual furnaces |50 are positioned `radiallyabout a center-post i5| and are secured to a platform i52 which rotates with the center-post 45| as drivenV in any suitable manner, preferably by means'of a variable speed drive mechanism to 10 regulate and entiol the speed of rotation of the furnaces |50. Since all of the furnaces are of likeicofnstruction, only one of them will be described. t t

Thefurnace |50 may consist of a metal crucibie les that is constructed or platinum or a piatinum alloy and has a plurality of nozzle orices |5`ii therein that are like the nozzle orifices I4. A high frequency coil I5? is provided around the furnace |50 to heat the Crucible inductivel'y and thus heat the glass therein. Y

The furnace |50 may be fed by the use of glass marbles E53 through the chute I5 extending from the hopper il. The glass marbles |58 are fed intermittently, depending upon the level of the molten glass in the Crucible |55.

The furnace ISG` is provided with the Contact member itil which is like the contact rod il of Fig. l and is adapted tc operate a solenoid |82 in the saine manner as the electric motor 4| is operated for controlling the feeding' of the glass strip 22 in Fig. 1. The electric circuit for operating the solenoid is the same electric circuit as for operating the motor tI illustrated in Fig. 3. As long as the electric circuit remains open, `the spring |33 in the solenoid |62 holds the gate ifl in retracted position to allow' continuous feeding of the mables |58. However, when the level of the molten glass rises to a point to engage the contact member ll, the solenoid t2 is energized to place the gate in the position illustrated in Fig. 5 and thus prevent further feeding of the mables |58 until the level of the molten glass is such as to be out of contact with the contact member IEI.

A collecting trough |10 for collecting the glass fibers or filaments I'II forms a circle around the furnaces |510, and is adapted to be driven by means of the gears |12 and |13. The gear |72 is suitably connected to a variable speed drive mechanism for controlling the rotating speed of the collecting trough |10. By controlling the speed of rotation of the furnaces |50, the degree of centrifugal force applied upon the body of molten glass inthe furnaces |50 is regulated to a value sufficient to obtain the desired exuding rate of the molten glass lthrough the -nozzle orifices |56. The speed of rotation of the collecting ring |10 is regulated relative -to the speed of rotation of the furnaces |50 to obtain the desired differential in speed of vrotation and obtain a desired rate of dravv upon the filaments III.

When starting to draw the filaments in the apparatus illustrated in VFigure 5, the filaments will initially attach 4themselves rto the collecting ring I, and will thereafter Abe drawn at a high rate of speed to obtain the desired iineness of diameterof the filaments.

'The variable factors previously set forth with regard to the apparatus disclosed in Fig. 1 affect the `drawing of Vfibers in the apparatus dis' closed in Fig. 5 in the same manner as hereto--V fore vreferred to, and the same general type` of controls can b e applied to the apparatus of Fig.

5 as hasbeen applied tothe apparatus shown in Fig. 1.

In the Vioregding description, the heating of the crucible II` has been referred to as being occa` sioned by ,high .frequency energy, which is preferable. However, other methods of heating the glass are within the scope of the invention as contemplated and the method specifically disclosed is by Way of explanation and `is not to ,be consideredlimiting. v. t t

While the apparatus disclosed and described einer herein constitute preferred forms of the invention, yet it will be understood that the method resulting from the operation of the apparatus is capable of variation without departing from the spirit of the invention, and that all modifications that fall within the scope of the appended claims are intended to be included herein.

Having thus full described my invention, what I claim as new and desire to secure by Letters Patent is:

' l. The method of producing continuous glass fibers of uniform diameter which comprises, feeding glass stock into a heating chamber having a plurality of apertures in one horizontal wall thereof of considerably larger size than the glass fibersv to be produced, heating the glass stock within the chamber by use of high frequency heating to maintain a supply of molten glass therein of uniform temperature in the mass adjacent the apertures, establishing a constant pressure differential between opposite sides of the body of molten glass disposed against said apertures of suihcient intensity to cause positive movement of the molten glass through the plurality of apertures at a constant rate in slowly moving streams attenuating the eXuded glass streams solely by a mechanical device moving at a constant rate and at high speed to produce continuous glass fibers of a determined and controlled diameter governed by the differential of rate of movement between the eXuded streams and the attenuated fibers.

2. The method of producing glass fibers which comprises, feeding glass stock into a heating chamber having a plurality of apertures in onev horizontal wall thereof of considerably larger size than the glass fibers to be produced, heating the glass stock within the chamber by use of high frequency heating to maintain a supply of molten glass therein, establishing a constant pressure differential between opposite sides of the body of molten glass in the chamber of sufficient intensity to cause positive movement of the glass through the plurality of apertures at a constant rate and form and maintain globule-like reservoirs of molten glass at the discharge end of each of the apertures in the heating chamber, and drawing an attenuated glass filament from eac-h of the globule-like reservoirs by a mechanical device moving at a constant rate and high speed during the attenuation of the bers.

3. The method of producing continuous glass fibers of uniform diameter which comprises, feeding glass stock into a heating chamber having a plurality of apertures in one horizontal wall thereof of considerably larger size than the glass fibers to be produced, heating the glass stock within the chamber by use of high frequency heating to maintain a Supply of molten glass therein at uniform temperature throughout the mass, establishing a gaseous pressure on one side of the body of glass that is greater` than the gaseous pressure on the opposite side of the body of glass at the apertures to exude the glass through the plurality of apertures under the effect of the differential of pressure between the said pressures, maintaining said pressure differential at a determined and constant Value to obtain a constant rate of movement of glass streams through the apertures, attenuating the glass streams into glass fibers by contacting the` glass fibers of the attenuated streams with a mechanical element moving at a high speed, said attenuation occurring between said chamber and said element, and effecting a cooling of the glass through the plurality of apertures under the effibers between the chamber and the element at agradual rate of temperature reduction from the temperature of the molten glass at said apertures to a temperature condition of the glas-s where due to solidication of the glass attenuation ceases solely by natural radiation of heat from the glass fibers under attenuation into the atmosp-here around the glass fibers occurring over a relatively long length of the bers between the chamber and said element.

4. The method of producing continuous glass bers of uniform diameter which comprises, feeding' 'glass stock into a heating chamber having a plurality of apertures in one horizontal wall thereof of considerably larger size than the glass fibers to "be produced, heating the glass stock within the chamber by use of high frequency heating to maintain a supply of molten glass therein at uniform temperature throughout the mass, establishing a gaseous pressure above the body of molten glass that is greater than the gaseous pressure below the apertures which added to the pressure of the head of glass above the apertures results in a total pressure effective on the body of molten glass to exude the glass fect of the said total pressure, maintaining said total pressure at a determined and constant value to' obtain a constant rate of movement of glass streams through the apertures, attenuating the glass streams into glass bers by contacting the glass fibers of the attenuated streams with a mechanical element moving at a high speed,lsaid attenuation occurring between said chamber and Y said element, and effecting a cooling of the glass bers between the chamber and the element at a gradual rate of temperature reduction from the temperature of the molten glass at said apertures to a temperature condition of the glass where due to solidification of the glass attenuation ceases solely by natural radiation of heat from the glass fibers under attenuation into the atmosphere around the glass fibers occurring over a relatively long length of the fibers between the chamber and said element.

5. The method of producing continuous glass fibers of uniform diameter which comprises, feeding glass stock into a heating chamber having a plurality of apertures in one horizontal wall thereof of considerably larger size than the glass bers to be produced, heating the glass stock within the chamber by use of high frequency heating to maintain a supply of molten glass therein at uniform temperature throughout the mass, establishing a gaseous pressure on one side of the body of glass that is greater than the gaseous pressure on the opposite Side of the body of glass at the apertures to exude the glass through the plurality of apertures under the effect of the differential of pressure between the said pressures, maintaining said pressure differential at a determined and constant value to obtain a constant rate of movement of glass streams through the apertures, attenuating the glass streams into glass bers by contacting the glass Iibers of the attenuated streams with a mechanical element moving at a high speed, said attenuationroccurring between said chamber and said element, effecting a cooling of the glass bers between the chamber and the element at a gradual rate of temperature reduction from the temperature of the molten glass at said apertures to a temperature condition of the glass where due to sclidication of the glass attenuation ceases solely by lnatural radiation of heat from the glass rangers "-bers under attenuation li'nto f the 'atmosphere around the glass iibersoocurringover a relatively "long flengthfoffthe' "bersl `between the chamber "andi said element-*and contrcrllingthe` diameter of4`the` attenuated bers by`establishing a co n stant rate bf movement of Vthefattenuated fibers "relative `-to the rate` ofmovenientat which the molten glass is eX-u'ded through said apertures.

6J The method ofp'r'oducing continuous glass be'rs of uniform diameterfw-hich comprises, feeding glass "stock" into a heating -Achamber having 'a plurality of apertures int-one 4horizontal"'Wall thereof 'of vconsiderablyl larger size than the glass -fbersto ibeproduced, heating "the 'glass stock Within the chamber byfuse` ofvhighv frequency *heatingfto-maintain a-4` supplyofmolten glass thereinf'at@ :uniform y temperature throughout the lmassfmaintainingthe temperature ofsaid heating "ichamber and' l the `molten glass l therein ati a constant value throughout themassof the chamb'er and the glass-to obtain the uniform temperafture condition-of the molten glass ineach` ofthe apertures', establishing a gaseous pressure on one iside-'of the body of glass that is greater than the-gaseous pressure on thefopposite-s'ide Yof the 1 =bodyof 'glass at the apertures to exude'the glass through-fthe 'plurality of apertures under" the *effectfiof the "differentialof `pressure between the 'said pressures; maintaining said pressure differ- Aentialat a determined and-constantvalue to obtain a" constant rate of movement of `glass streams through Tthe i apertures attenuating the glass Fstreams into glass fibers by-contacting the glass "fibers-of-theiattenuated" streams fwith a` mechanical element moving `at a high speed, said attenuation i occurring between said cl'iamber and fsaid element;`eifectin`g acooling of theglass' fibers 4b 'etweenthe chamber and the element at a gradualrate `of tempera-ture reduction from the temperature of themolten 4glass atfsaid apertures "to atemperature condition-`of thev glass where due" to solidication off-` the glass? attenuation "ceases solely by natural radiati4 on "of heat from the iglass' bers -under attenuation into'theatmosphere "around-"the glass" fibers occurring over, a rela- Y`"tive'lylo'nglength of the ib'ersbetween the chamber andisaid element, and correlating the factors fbfpressure" differential', temperature of the `body fof'mlten vglass" and speedi of "attenuation of the 'lglaissfflberslrelative to the sizeof the'aperture "through which the-'glass is exuded'to establishland `to "maintaina determined controlled diameter "of attenuated fiber.

71" The method of producingcontinuous glass 'b'ers of uniform-diameter which comprises, heating `glass "stock within a chamber 'having a uniform transverse cross-section from" a' central point "thereofby means] of the- -use "ofhigh frequency -ringbetw`een said chamber andl said element'jand effecting acooling of the glass vfibers between* the chamber and the element at a gradual rate of temperature "reduction `from the temperature '-bf A:thenilten glass at said aperturesLto atempera- `"ture conditionof the 'glasswhere due to solidi- Aication `of the glass l attenuation ceases l solely -by natural radiation of heat from the glass fibers un- Tderf attenuation Jinto the atmosphere around the glass fibers occurring over a relatively long length of `the fibers `between thelchamber f and said -e`1ef ment.

Y 8:' The' method or producing continuous "glass- 1bers of*` uniform diameter which comprises, feeding glass stock into a heating chamber having aplurality of apertures in one horizontal Wallthereof of considerably larger size than the glassbersto -beeproducedjheating the glass stock withinthe chamber by use of high frequencylheating-i to frnaintain a supply of Vmolten glass therein at 'uniform temperature throughoutlthe mass, establishing a gaseous pressure on one side ofthe body `oli-"glass that is `greater than the gaseous pres- 'surei-ontheopposite side of thebody of1"glass 'atthe "apertures to exude' the glass through-the 4plurality of apertures under the effect of the differential of pressure between the said pressures, maintaining said pressure differential at a determined and constant valueto obtaina constant rate of 'movement of Vglass streamsthrough the apertures, attenuating the glass streams into glass Aiibersfby contacting the glassiibersof the attenuated streams with-a' mechanical element 'moving at a high speed; said attenuation occurring `between said chamberdandsaid element, effecting a` cooling of *the -glass fibers' between 'the chamber andthe element at a gradual rate "bftemp'erature reduction from the temperature of the molten glass at said apertures to a tem- `perature condition of the "glass Where due to solidification of the `glass attenuation ceases-solely "by natural-radiation of heat from the glass fibers under attenuation into the atmosphere around Athe glass b'ersoccurring over a relatively long length of the bers between `the chamberand saidelemenu and maintaining constant? the heatting eifect on thechamber and thepressurefdifferential on the glass body while varying Athe speedof movement of the attenuated fiber to Aob- *tain' alA controlled change in the diameter of the 'attenuated uber. 1

""9.` The'method of producing'continuous glass fibers of uniform diameter which comprises, feeding glass stock into a `heating chamber having a plurality of `apertures Vinone horizontal Wall thereof "of considerably larger size than the glass fibers to `be: produced, heating the glass stock Within the chamber by use of high frequency heating to maintain a supply of molten glass therein at uniform temperature throughoutthe mass; establishing a gaseous pressure on one side `of the body of glass that is greater than. the gaseous pressureonfthe opposite side of the body 'of glassat the apertures to` exude the glass through the plurality of apertures under the effect 'of the differential of pressure between the saidpress'ures; maintaining said pressure 'differrentialat a determined and constant value to obtain a constant rateof movement of glass streams `through the apertures, attenuating the glass `strearnsinto glass 'fibers Aby contacting the glass `fibers-'ofthe attenuatedstreams With a mechanical-element moving at a high speed, said attenuation occurring between said chamber and said `element,Y `effecting' a cooling of the. glass 'bers betvveenthechamber and the element at a `l gradual'"rate of temperature reductionfrom the temperature of themolten glass 'at said apertures to a temperature, condition of the glass where due to solidication of the glass attenuation ceases solely by natural radiation of heat from the glass fibers under attenuation into the atmosphere around the glass fibers occurring over a relatively long length of the fibers between the chamber and said element, and maintaining constant the speed of movement f the attenuated ber and the pressure dierential on the vglass body while varying the heating eiect on the chamber to obtain a controlled change in the diameter of the attenuated ber.

10. The method of producing continuous glass bers of `uniform diameter which comprises, `feeding glass stock into a heating 'chamber having ia plurality of apertures in one horizontal vwall .thereof of considerably larger size than the glass fibers to be produced, heating the glass stock within the chamber by use of high frequency .heating to maintain a supply of molten glass therein at uniform temperature throughout the mass, establishing a gaseous pressure yon-one side of the body of glass that is greater than the gaseous pressure on the opposite side of the body of glass at the apertures to exude the glass through the plurality of apertures under the effect o-f the diiferential of pressure between the said pressures, maintaining said pressure differential at a det-ermined and constant value to obtain a constant rate of movement of glass streams through the apertures, atte-nuating the glass streams into glass fibers by contacting the glass bers of the :attenuated streams with a mechanical element moving `at a high speed, said attenuation occurring between said chamber and said element, effecting a cooling of the glass bers between the chamber and the element at a gradual rate of temperature reduction from the temperature 0f the molten glass at said apertures to a temperature condition of the glass where due to solidilcation of the glass vattenuation ceases soleli by natural radiation of heat from the glass bers under attenuation into the atmosphere around the glass fibers occurring over a relatively long length of the fibers between the chamber and said element, and maintaining lconstant the heating effect o n the chamber and the speed of movement of the attenuated fiber while varying the pressure differential on the glass body to obtain a controlled change in the diameter of the attenuated fiber.

11. The method of producing continuous glass bers of uniform diameter which comprises, feeding glass stock into a heating chamber having a plurality of apertures in one horizontal wall thereof of considerably larger size than the glass bers to be produced, heating the glass stock within the chamber by use of high frequency heating to maintain a supply olf molten glass therein at uniform temperature throughout the mass, establishing a gaseous pressure on one Iside of the body of glass that is greater than the gaseous pressure on the opposite side of the body of glass at the apertures to exude the glass throughj the ,plurality of apertures under the effect of the diferential of pressure between the said pressures, maintaining said pressure differential at a determined and constant value to obtain a constant rate of movement of glass streams throughv the apertures, attenuating the glass streams into glass bers by contacting the glass fibers of the lattenuated streams with :a mechanical element moving at a high speed, said attenuation occurring between said cham-ber and said element, effecting a cooling of the glass fibers between the chamber and the element at a gradual rate of '16 temperature reduction from the temperature of the molten glass at said apertures to a temperature condition of the glass where due to solidification of the glass attenuation ceases solely b-y natural radiation of heat from the glass fibers under attenuation into the atmosphere around the glass bers occurring over a relatively long length of the fibers between thechamber and said element, and coordinating the factors of pressure diiferential, heat applied to the heating chamber, and the rate of attenuation 4of the fibers :at relatedV values to regulate the diameter of the attenuated bers eas governed by the differential of rate of movement between the exuded lstreams and the attenuated fibers under the yparticular condition of fluidity of the glass as controlled by the heat applied Ato the heating chamber.

v12. The method of producing continuous glass bers of uniform diameter which comprises, feeding glass stock into a heating chamber having a plurality of apertures in one horizontal wall thereof of considerably larger size than the glass fibers to be produced, heating the glass stock within the chamber by use of high frequency heating `to maintain a supply of molten glass vtherein-at uniform temperature throughout the mass, establishing a gaseous pressure on one-,side of the body of glass that is greater than the .gaseous pressure on the opposite side of the body of 'glass at4 the apertures to exudev the glass through the lplurality `of apertures under the effect `ofthe differential of pressure between the -said pressures, maintaining saidA pressure differential tween. the-chamber and the element lat a gradual rate of temperature reduction from the tempera- `ture -of the molten` glass at said apertures to la temperature condition of the glass where due to solidiflcation of the glass attenuation ceases solely by natural radiation of heat from the glass bers under attenuation into the atmosphere around the glass bers occurring over a relatively long length of the fibers betweenthe chamber and said element, coordinating the factors of pressure diiferential, heat applied to the heating chamber, and the rate of attenuation of the fibers latrelated values to regulate the diameter of the-attenuated fibers as governed by the diiferential .of rate of movement between the exuded streams and the attenuated fibers under theparticular condition `of fluidity' of the glass as controlled" by the heat applied to the heating chamber, and thereafter maintaining these `factors constant to maintain a constant diameter of the drawn'lber.

EVERETT J. COOK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS l' Number Name i Date 2,187,094 Pink Jan. 16, 19 2,219,346 Thomas et al Oct. 29, 1940 2,229,489 Barnard Jan. 2l, 1941 2,234,986 Slayter Mar. 18, 1941 2,294,266 Barnard Aug. 25, 1942 

1. THE METHOD OF PRODUCING CONTINUOUS GLASS FIBERS OF UNIFORM DIAMETER WHICH COMPRISES, FEEDING GLASS STOCK INTO A HEATING CHAMBER HAVING A PLURALITY OF APERTURES IN ONE HORIZONTAL WALL THEREOF OF CONSIDERABLY LARGER SIZE THAN THE GLASS FIBERS TO BE PRODUCED, HEATING THE GLASS STOCK WITHIN THE CHAMBER BY USE OF HIGH FREQUENCY HEATING TO MAINTAIN A SUPPLY OF MOLTEN GLASS THEREIN OF UNIFORM TEMPERATURE IN THE MASS ADJACENT THE APERTURES, ESTABLISHING A CONSTANT PRESSURE DIFFERENTIAL BETWEEN OPPOSITE SIDES OF THE BODY OF MOLTEN GLASS DISPOSED AGAINST SAID APERTURES OF SUFFICIENT INTENSITY TO CAUSE POSITIVE MOVEMENT OF THE MOLTEN GLASS THROUGH THE PLURALITY OF APERTURES AT A CONSTANT RATE IN SLOWLY MOVING STREAMS ATTENUATING THE EXUDED GLASS STREAMS SOLEY BY A MECHANICAL DEVICE MOVING AT A CON- 